# this stuff is from Beginning Game Development with Python and PyGame

import math
class Vector2(object):
    def __init__(self, x=0.0, y=0.0):
        self.x = x
        self.y = y
    def __str__(self):
        return "(%s, %s)"%(self.x, self.y)
    @classmethod
    def from_points(cls, P1, P2):
        return cls( P2[0] - P1[0], P2[1] - P1[1] )
    def get_magnitude(self):
        return math.sqrt( self.x**2 + self.y**2 )
    def normalize(self):
        magnitude = self.get_magnitude()
        self.x /= magnitude
        self.y /= magnitude